The antifungal activity of the natural product 6-pentyl-2H-pyran-2-one (6-PAP) is well known and the in vitro activity of this compound against a range of phytopathogens has been reported (1, 2, 3, 4). Early structure-activity studies indicated that minor structural modifications to 6-PAP yielded compounds with reduced antifungal activity (5).
Prior to its identification as a natural product, the chemical synthesis of 6-PAP and its structural analogs received attention because of the potent organoleptic properties of these compounds (6, 7). However, despite the attention paid to the synthesis of 6-PAP by these and other methods (8, 9), its preparation remains costly.
As an organic natural product 6-PAP is innately biodegradable. Combined with its established use as a food additive and assumed low toxicity 6-PAP is an attractive candidate for development as an agricultural/horticultural fungicide. However, its cost is an obstacle to further development.
The applicants have now surprisingly found that a structural analog of 6-PAP, namely 4-methyl-6-pentyl-2H-pyran-2-one, has fungicidal activity similar to that of compound 6PAP. The applicants have also found that 4-methyl-6-pentyl-2H-pyran-2-one can be prepared with relative ease and economy as compared to preparation of 6-PAP. It is towards the use of 4-methyl-6-pentyl-2H-pyran-2-one as a fungicide that the present invention is directed.